Non-toxic invert analog glass compositions of high modulus

ABSTRACT

Glass compositions having a Young&#39;&#39;s modulus of at least 15 million psi and a specific modulus of at least 110 million inches consisting essentially of, in mols, 15-40% SiO2, 6-15% Li2O, 2445 percent of at least two bivalent oxides selected from the group consisting of Ca, ZnO, MgO and CuO; 13-39 percent of at least two trivalent oxides selected from the group consisting of Al2O3, Fe2O3, B2O3, La2O3, and Y2O3 and up to 15 percent of one or more tetravalent oxides selected from the group consisting of ZrO2, TiO2 and CeO2.

3/1971 Bacon .11. 106/52 United States Patent 11 1 1111 3,811,901 Bacon [4 May 21, 1974 [5 1 NON-TOXIC INVERT ANALOG GLASS 3,060,041 /1962 Lowenst'ein 106/50 COMPOSITIONS OF I MODULUS 3,183,104 5/1965 Thomas 106/50 3,484,259 12/1969 Lewis et a1 106/50 Inventor: James Bacon, Manchester, Com 3,166,428 1/1965 Thomas 106/50 [73] Assignee: United Aircraft Corporation, East I Hartford, Conn. Primary Examiner-Helen M. McCarthy Filed p 21 1972 Attorney, Agent, or Firm.l0hn D. De] Ponti [21] Appl. No.: 243,294 ABSTRACT Related .8. Application Data. [63] Continuatiomim an of Ser No 874 673 Nov 6 Glass composmons having a ifoungs modulus of at 1969 abandon? least 15 m1l110n ps1 and a spec1fic modulus of at least million inches consisting essentially of, in mols,

[5 l 1 (363C 3/04 two bivalent oxides selected from the group consisting [58] Fie'ld /5O 52 54 of Ca, ZnO, MgO and CuO; 13-39 percent of at least two trivalent oxides selected from the group consisting References of A1203, F6203, B203, 1.43. 0 an? Y203 UpItO percent 0 one or more tetrava ent 0x1 es se ecte UNITED STATES PATENTS from the group consisting of ZrO T10 and CeO 2,805,166 /1957 Liiffler 8 Claims, No Drawings NON-TOXIC INVERT ANALOG GLASS COMPOSITIONS OF HIGH MODULUS BACKGROUND OF THE INVENTION This application is a continuation-in-part of application Ser. No. 874,673 filed Nov. 6, 1969 by the same inventor and now abandoned.

The invention described herein was made in performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 USC 2457).

This invention relates to high modulus glass and glass compositions and more particularly relates to invert glasses having a Youngs modulus of at leastmillion psi, a specific modulus of at least 110 million inches and containing no toxic elements.

In the present age, there has been a continuing search for glasses of high modulus and low density, capable for use as reinforcements, preferably in fiber form, in composite structures ranging from high strength missile cases and helicopter blades to propeller spinners and gas turbine engine parts. Glass offers promise as the reinforcements in such applications since it may be quickly and cheaply produced by relatively conventional techniques and, generally, presents no compatibility problems with the matrix materials with which it is normally used. There is a need however, to-provide glass formulations which possess a high modulus of elasticity, and preferably a high modulus-density ratio. It is even more preferable if the glass possess the afore mentioned two characteristics in combination with an appropriate liquidus-viscosity relationship to permit fiberization. Furthermore, in most commercial applications, it is important that the glasses contain no toxic elements, such as beryllia or thoria, which may present complications either in their manufacture or in their use.

SUMMARY OF THE INVENTION The glass compositions of the present invention are a high modulus, low density invert glass which, in their preferred form consist essentially of a combination of silica, the monovalent oxide of lithium, two or more bivalent oxides selected from the group consisting of CaO, ZnO, MgO and CuO, and at least two trivalent oxides selected from the group consisting of A1 0 F6203, B 0 La o and Y O More particularly, the inventive glasses contemplated are those having a Youngs modulus of at least 15 million psi and a specific modulus of at least 1 10 million inches which consists essentially of l540 mol SiO 6-15 mol Li O, 24-45 mol percent of at least two bivalent oxides selected from the group consisting of CaO, ZnO, MgO

and CuO, 13-39 mol percent of at least two trivalent.

oxides selected from the group consisting of A1 0 Fe O B 0 La O a and Y O and up to 15 mol percent of one or more tetravalent oxides selected from the group' consisting of ZrO TiO and CeO It will be noted that the glasses are comprised of only one alkali oxide and a combination'of alkaline earth oxidesand trivalent and tetravalent oxides.

Preferably, the inventive glassesare those having a Young's-modulus of at least 15 million psi and a specific modulus of at least 1 l0 million inches which consists essentially of 1'5-40 mol SiO 6-15 mol Li O,

specific modulus of at least million psi that arereadily formed into fibers having a relatively high fiber modulus, above 13 million inches, are described. These include glasses consisting essentially of about, in mols:

25% SiO 12% M 0, 12% MgO, 12% ZnO, 12% A1- 0 15% B 0 and-12% Y O 25% SiO 5% Li O, 20% MgO, 9% CaO, 2% CuO,

I AI203, B203, and TiO 25% SiO;, 5% Li O, 20% MgO, 6% CaO, 2% CuO,

8% A1 0 3% relo 14% Y O and 3% TiO 25% SiO 6% Li O, 20% MgO, 15% CaO, 4% ZnO, 2% CuO, 13% B 0 12% Y O and 3% TiO and 25% SiO 15% Li O, 15% MgO, 15% CaO, 10%

ZnO, B203, Y O

In the middle three formulations, the glass has a Youngs modulus above 17 million psi, a specific modulusabove million inches and yield fibers having a fiber modulus of approximately 16 million psi.

In several other preferred embodiments, formulations having a Youngs modulus of at least 20 million psi and a specific modulus of at least million inches are described. These include glasses consisting essentially of about, in mols:

24% SiO 12% Li O, 16% MgO, 12% CaO, 8% ZnO 3% A1 0 10% B 0 12% ZrO and 3%TiO 22% SiO 11% M 0, 22% MgO, 11% ZnO, 11% A1- 0 12% Y O and 11% ZrO and 25% SiO 15% Li O, 15% MgO, 15% CaO, 15%

ZnO, AIgOg Y O The first of the above three glasses exhibits a Youngs modulus in excess of 22 million psi with a specific modulus of 200 million inches.

The features of the present invention will be discussed in greater detail in the description which follows and will become more evident therefrom to those skilled in the art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS and several kinds of alkaline earth oxides but do not include any trivalent oxides, the glasses of the present invention contain so little silica that a continuous silica network is not possible. It will be appreciated that such glasses may be characterized by a structural parameter 1 which denotes the average number of bridging 0 ions. According to a rule of Zachariason for silicate glass formation, which postulates that these silicate glasses should have a three-dimensional network in which the S10, tetrahedra share approximately three of Contribution to Young's their four oxygens with neighboring tetrahedra, commdulus mercial silicate glasses have Y values between 3.0 and $10, 7.3 3.5. For ternary soda lime silica glasses it is not possible 2' a 12.6 to lower appreciably the parameter Y below 3.0 and Lip 70 still obtain stable glasses. In contrast, the strongly ba- 1 ZnO l.72 and r1s1ng s1c or mvert glasses of this 1nvent1on generally have Y with mere values of 2.0 or below and in some cases values of zero. To ing 11,0 In calculating the parameter Y, the following formula a; is used: I 1 MgO 12.0 and rising with decreasing R10 and 510,10 14.8 "3 iii a Y zoo/P 1 18.6

. It has thus been found that the judicious use of the where P mol SiO It is readily seen that for an orheavier oxides is obviously to be considered in cases thosilicate such as Na,SiO, with 33 75 mol percent 810,, h re they mp e ty, r a te orking Y has a value of 0 while a meta silicate with a 40 mol range and other characteristics. percent siOz, Yhas a value of 1.0 and leads to the for- It is to be noted that several rules which are predimation of :1 tetrahedra. As will be seen hereinafter, all Gated on experience with glasses comprised of silica of the glasses of this invention have a total SiO content etworks do not hold true for the non-network invert of less than 50 mol percent, more precisely 40 mol perglasses. It has, for example, been found that substitu- .cent or less, and in some cases as little as 15 percent. tion of 2 3 for z fails to decrease he density While It thus becomes apparent that the prior concept that the substitution of CuO for ZnO markedly lowers the silicate glasses must have a three-dimensional network dcnsuy. of S10, tetrahedra cannot be maintained, even if the All Of the compositions investigated were made by network modifiers are cations of the noble gas type. It melting 500 gram batches of the specified raw materiis therefore considered that the present glasses lie beals in high purity (99.9 percent) alumina crucibles in tween the tetrahedral structures of the conventional air using kilns heated by Super-Kanthal hairpin electrisoda lime silicate glasses and the octahedral structures cal resistance elements. The starting materials used of some special glasses such as the Morey-Eastman were 5 micron particle-size high purity silica, high pu- Kodak optical glasses. In any event, the advantages of rity alumina of 325 mesh, laboratory reagent grade the present glasses will be recognized, not only because 3 5 magnesium oxide, 99.9 percent lanthanum oxalate, and of their consistently high Youngs modulus, specific .other comparable materials such as reagent grade zinc modulus and in some cases, ready fiberizability, but carbonate or calcium carbonate. These materials also because they permit lowering of the liquidus temyielded a water-white optical grade glass free of seed, perature, greatly increase the field of glass formation stone and bubbles when properly compounded and and allow the study of the effect of the atomic structure held at temperatures of 1,000-l,650C for at least 2 of a glass upon its properties. As indicated above, inhours. With the above technique, alumina crucibles of vert glasses have been made according to the present even slightly lower purity (99.3-99.7 percent) cannot invention with an elastic modulus in excess of 20 milbe used. It is recognized however that the glasses may lion pounds per square inch. U w V g be prepared in beryllia crucibles in air and in the same It has been determined that while low atomic number h or P m cnlcibles' in in a Platform kiln oxide components are a primary choice in achieving 01 In tungsten CtUClblCS 1n pur1fied argon Ol' vacuum athigh modulus glass compositions of high specific modumosphereslus, they are not the only choice since contributions per The composl'flonfi of some of h r presentauve mol r nt t Young's odul of v l of th glasses formulated 1n the course of the experimental heavier elements were high, as follows: Program are Set forth In Table WW, Table l Compositions of Representative Glasses (Mol Percent) Example 510 up (3110 ZnO MgO CuO A1,0 mo, 13,0, 141,0, Y,0 zro, T10, CeO,

1 40 12 12 12 12 12 2 40 12 12 12 12 12 3 25 15 15 15 15 s 7 4 25 12 12 12 12 15 12 5 1s 15 15 15 15 a 10 7 6 22 11 11 22 11 12 11 7 39 6 6 24 12 3 10 s 39 6 p 24 3 12 6 10 9 24 12 12 8 l6 3 10 12 3 10 20 1.2 12 s 16 6 14 12 11 25 5 9 2o 2 s 14 14 3 12 25 5 6 20 2 s 3 14 14 3 13 25 10 15 10 15 13 12 14 25 7 15 a 15 13 12 15 25 6 15 4 20 2 13 12 3 1 H 9 :1 2 3 Table l :Q ontinued Compositions of Representative Glasses (Mol Percent) Exam 16 510, L1 CaO ZnO MgO CuO 41.03 86.03 13,0 [.3 0 v.0 ZrO T10 C60 Table I A E (Weight Percent) ample SiO Li,O CaO ZnO MgO CuO A1203 F6203 B20, La O YZOS ZrO, TiO CeO In order to characterize the var1ous glasses, measure- Table ll ments of the density and Youngs modulus of bulk samples as well as Youngs modulus of mechanically drawn Glass Deng" s Mdulus S M v Density Youngs Modulus Specific Modulus fibers were made. As a standard denslty measuring Example 115/111. psi x 10 10 in.

technique, the heavy-liquid-of-known density comparison procedure was used for samples wlth denslties less 2 0,1347 [34 v 137 than 3.00 gms/cm while the Archimedean method was 3 041275 203 employed for samples with densities greater than 3.00 g 815?? :3; :3: gms/cm 6 0.1095 20.7 189 Bulk sample for modulus measurement were preg g-Egg :3; {1g pared using the technique whereby the samples were 9 0:1 136 22:8 200 drawn directly from the crucibles of molten glass into 1? gig; 13g fused silica tubes previously dusted lightly with pow- 12 011220 1 140 dered magnesia. Controlled suction for pulling the sam- 13 188 113-2 ple into the tube was supplied by a hypodermic syringe. l; 8:325 :21? Since all of the experimental glasses had coefficients of 16 0.1212 17.8 146 thermal expansion at least higher than that of fused sil- 883g :23 ica, the aspirated bars shrank away from the tube upon 19 011365 l8:l 132 cooling and thus were readily removable. 3? 31 :2; Table II lists the values for a number of glasses made 22 011242 3 140 and tested in accordance with the teachings herein. 23 (11215 138 As is evident from the Tables, several of the formulag; 8153: tions have proved to display extremely high modulus as 26 0.1105 16:] 146 well as modulus/density ratios superior to the best of gm; g

glass compositions heretofore known. The particular formulation selected in a given application, however, will be dependent usually not only upon the properties of the end product but also upon the cost of the ingredients included. This is particularly true in commercial production.

Several of the glasses proved to be fiberizable. In order to evaluate these glasses, a poor man s bushing was used to prepare mechanically drawn fibers. The bushing comprises a 20 cm platinum crucible with a reinforced bottom and central orifice. The orifice is formed by welding several thicknesses of platinum foil to the bottom of a normal platinum crucible until a bottom thickness of three-sixteenths in. is obtained. A central orifice 0.088 in. at top, 0.063 in. at bottom and three-sixteenths in. long in the crucible is made by taper reaming. Once the orifice is made, the crucible is filled with glass andintroduced into a platform furnace having high temperature Super-Kanthal hairpin heating elements together with a first ring orifice to provide water cooling immediately below the crucible and a second ring orificeto cool the fiber with helium jets as it forms. The fibers were drawn at speeds of 4,0008 ,000 feet/minute and yielded circular glass fibers having a diameter of approximately 1 mi]. The fibers were then evaluated on an Instron CRE tester operated with a machine speed of 0.2 in./minute, a chart speed of 20 in./minute, a gage length of in. and a full scale capacity of 1.0 lb. The specimens were held in air actuated clamps with flat rubber coated faces. Table 111 lists the valuesfor several glasses which were mechanically drawn into fibers.

Table III Fiber Modulus Youngs Modulus Example psi X 10 La O (lower molecular weight trivalent oxides of v Group "18) are preferred in comparison to Nd,0,,

Sm O 0:1,0, and En O Similarly, the lower molecular weight tetravalent oxide SiO, is preferred to GeO,, SnO, and PhD, and the lower molecular weight tetravalent-.oxidesTiO, and 2:0 of Group WE are to be preble, and the field strength of the ions as high as possible.

Of course, the glass compositions may contain certain additional tetravalent or sesquivalent oxides or fiuorides commonly employed in optical glassmaking such as tantalum pentoxide (Ta,O or tungsten trioxide (W0 in slight amounts.

While the invention has been described in connection with a number of particular preferred embodiments, they are considered illustrative only and no limitation is intended thereby. Various alterations and modifications will be evident to those skilled in the art within the true spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

l. A fiberizable glass composition having a Youngs modulus of at least 15 million psi and a specific modulus of at least million inches consisting essentially of about, in mols:

25% SiO 12% L1 0; 12% MgO; 12% ZnO; 12%

A1103; and 0 2. A fiberizable glass composition having a Youngs modulus of at least 17 million psi and a specific modulus of at least million inches consisting essentiallylus of at least 140 million inches consisting essentially of about, in mols:

25% $0,; 6% Li O; 20% MgO; 15% CaO, 4% ZnO;

2% CuO; 13% B 0 12% Y,O and 3% TiO-,.. 5. A fiberizable glass composition having a Youngs modulus of at least 16 million psi and a specific modulus of at least 140 million inches consisting essentially of about, in mols:

25% SiO 15% U 0; 15% MgO; 15% CaO; 10%

ZnO; 15% B 0 5% Y,o,.

6. A glass composition having a Youngs modulus of at least 20 million psi and a specific modulus of approximately 200 million inches consisting essentially of about, in mols:

24% SiO=; 12% L1 0; 16% MgO; 12% CaO; 8% ZnO;'

7. A glass composition having a Youngs modulus of at least 20 million psi and a specific modulus of approximately 189 million inches consisting essentially of about, in mols:

22% SiO,; 11% Li,0; 22% MgO; 11% ZnO; 11%

A1103; Ygog and ZrO,.

8. A glass composition having a Youngs modulus of at least 20 million psi and a specific modulus of approximately 159 million inches consisting essentially of about, in mols: 25% SiO,; 15% Li,0; 15% MgO; 15% C510, 15%

' A1103 and Ygoa.

i I! III II 4' 

2. A fiberizable glass composition having a Young''s modulus of at least 17 million psi and a specific modulus of at least 140 million inches consisting essentially of about, in mols: 25% SiO2; 5% Li2O; 20% MgO; 9% CaO; 2% CuO; 8% Al2O3; 14% B2O3; 14% Y2O3 and 3% TiO2.
 3. The glass composition of claim 2 wherein said CaO content is 6 percent and Fe2O3 is present in an amount of 3 percent.
 4. A fiberizable glass composition having a Young''s modulus of at least 17 million psi and a specific modulus of at least 140 million inches consisting essentially of about, in mols: 25% SiO2; 6% Li2O; 20% MgO; 15% CaO, 4% ZnO; 2% CuO; 13% B2O3; 12% Y2O3 and 3% TiO2.
 5. A fiberizable glass composition having a Young''s modulus of at least 16 million psi and a specific modulus of at least 140 million inches consisting essentially of about, in mols: 25% SiO2; 15% Li2O; 15% MgO; 15% CaO; 10% ZnO; 15% B2O3; 5% Y2O3.
 6. A glass composition having a Young''s modulus of at least 20 million psi and a specific modulus of approximately 200 million inches consisting essentially of about, in mols: 24% SiO2; 12% Li2O; 16% MgO; 12% CaO; 8% ZnO; 3% Al2O3; 10% B2O3; 12% ZrO2 and 3% TiO2.
 7. A glass composition having a Young''s modulus of at least 20 million psi and a specific modulus of approximately 189 million inches consisting essentially of about, in mols: 22% SiO2; 11% Li2O; 22% MgO; 11% ZnO; 11% Al2O3; 12% Y2O3 and 11% ZrO2.
 8. A glass composition having a Young''s modulus of at least 20 million psi and a specific modulus of approximately 159 million inches consisting essentially of about, in mols: 25% SiO2; 15% Li2O; 15% MgO; 15% CaO, 15% ZnO; 8% Al2O3 and 7% Y2O3. 